The present invention pertains to a junction for orthogonally oriented waveguides, with a transformation stage containing a first oblong opening for connecting a first waveguide which is designed to carry a first type of ground wave, and having a second oblong opening for connecting a second waveguide which is designed to carry a second type of ground wave, where the first oblong opening and the second oblong opening are oriented orthogonally with respect to each other.
The known junctions of this type are realized, for example, by means of a combination of several waveguide segments which are rotated with respect to each other. A description of a junction of this type is found, for example, in the xe2x80x9cTaschenbuch der Hochfrequenztechnik (Pocket Manual of High Frequency Technology), Meinke/Grundlach, 2nd edition, pages 399 ff.xe2x80x9d The production of such a junction from several waveguide segments is very expensive, however, and an additional problem is that junctions of this type cannot be used in so-called integrated waveguide circuits which are realized using the half-shell technique.
An additional junction of this type which could be produced in principle using the half-shell technique is known from EP 0392999B1. This publication pertains to a field-rotating waveguide junction in waveguides for electromagnetic microwaves, where the junction has at one of its ends a quasi-rectangular cross section of the desired height and width, with the shape of the cross section differing from rectangular by a fin which projects into the junction from one side of the cross section in the height direction of the cross section, and where the junction has at its other end a rectangular cross section with one long side and one short side. EP 0392999B1 provides for the waveguide junction to have a first part which extends from one end of the quasi-rectangular cross section to a central segment with L-shaped cross section, and a second part which extends from the central segment to the other end of the rectangular cross section; the height extension of the fin which projects inward at the one end of the waveguide junction is oriented in essentially the same direction as the long side of the rectangular cross section at the other end of the waveguide junction; and the dimension of the L-shaped central segment is smaller on one side of the fin than the quasi-rectangular cross section, and on the other side of the fin its dimension is greater by a corresponding degree than that of the quasi-rectangular cross section in the height direction of the inward-projecting fin. The junction in accordance with EP 0392999B1 is also assembled from several waveguide segments with various cross section geometries. The production of this junction is expensive, however, and the necessary overall length of the construction is relatively great, which is disadvantageous in particular in conjunction with integrated waveguide circuits.
The fact that the junction according to the invention provides for the transformation stage to have an essentially right-angled geometry with a height, a width and a depth, where the height and the width are chosen such that both the first type of ground wave and the second type of ground wave can be propagated in the transformation stage, creates a compact, easily manufactured junction of relatively small overall length which matches the ground wave types of two orthogonally oriented waveguides across a broad range of frequencies with little reflection. The construction according to the invention causes the formation of a hybrid wave type in the transformation stage, by means of which a transformation between the first ground wave type and the second ground wave type is achieved. The junction according to the invention can be integrated for example as a subcomponent in planar waveguide circuits. Because of the rotation of polarization which is possible within a total structure with the junction according to the invention, with complex integrated waveguide circuits the optimal installation position and coupling can be achieved for each component. In spite of the short overall length which is possible with the junction according to the invention, very good electrical properties are attained over a very broad range of frequencies. In addition, because of the very short possible overall length, a very compact overall structure can be achieved with complex integrated waveguide circuits, for example with the distributor networks for array antennas described in EP 0392999B1 mentioned at the beginning, where several of the junctions of this type are needed. By preference there is provision for the transformation stage to have a length or depth xe2x89xa6(2n+1)xcex/4, with n=0, 1, 2, 3 . . . , where xcex is the waveguide wavelength of the H10 or H01 wave type in the area of the transformation stage. Such a length or depth of the junction according to the invention makes possible optimal transport of energy, where the shortest and preferred possible length or depth is approximately xcex/4. In particular if the width and height of the transformation stage have similar dimensions, the corresponding threshold wavelengths xcexiH01 and xcexiH10, and thus the waveguide wavelengths of the wave types H10 and H01 in the area of the transformation stage, are similar. With xcexH01≈xcexH10, the length of the transformation stage is then txe2x89xa6(xcexH01+xcexH10)/8≈xcexH10/4≈xcexH01/4. Furthermore, xcex can be the mean waveguide wavelength of the useful frequency band of the first and second waveguides.
The first oblong opening is preferably located in the front face of the transformation stage, and the second oblong opening is preferably located in the rear face of the transformation stage.
At the same time, the first oblong opening can be positioned horizontally in the upper or lower part of the front face of the transformation stage.
With certain implementations, the length of the first oblong opening can correspond approximately to the width of the transformation stage. This makes particularly good sense when the first waveguide is connected to the transformation stage directly, that is, without an intervening shield and without an additional transformation stage.
The second oblong opening is preferably positioned vertically in the left or right area of the rear face of the transformation stage. Particularly good results are obtained if the second oblong opening is positioned immediately adjacent to the left or right edge of the rear face of the transformation stage.
In certain variants, the length of the second oblong opening can correspond approximately to the height of the transformation stage. This solution suggests itself in turn when the second waveguide is connected to the transformation stage directly, that is, without an additional transformation stage.
To increase the bandwidth, in certain variants of the junction according to the invention there can be provision for the first opening to be connected to an additional transformation stage which is provided for connecting the first waveguide.
In that case, the additional transformation stage can be arranged symmetrically to the cross section of the first waveguide and asymmetrically to the transformation stage. Variants are also conceivable, however, in which the additional transformation stage is arranged with an entirely different symmetry or asymmetrically, depending on the overall construction.
If an additional transformation stage is employed, its width can be smaller than that of the transformation stage.
Naturally, it is also conceivable for an additional opening to be associated also, or only, with the second opening.
Furthermore it is conceivable for the first opening to be combined with a first shield which is provided for connecting the first waveguide. This first shield can also contribute to increasing the bandwidth of the junction.
Although this is not absolutely necessary, the width of the first shield can be smaller than the width of the transformation stage, depending on the transmission performance desired.
To further enlarge the bandwidth, the second opening can be combined with a second shield which is provided to connect the second waveguide.
The width of the second shield can then be smaller than the height of the transformation stage.
Since the junction according to the invention can be realized by means of the half-shell technique, it can be manufactured in a simple manner, for example by a milling procedure.
Furthermore, the junction according to the invention can be formed by an integrated waveguide circuit, or can be a component of such an integrated waveguide circuit.
The first waveguide and the second waveguide can have different cross section dimensions, if appropriate. For example, on one side a standard waveguide could be connected (width: height≈1:2), and on the other side a waveguide with reduced width (width: height≈1:4). In this connection it is also conceivable for the first and the second waveguides to be formed by two different standard waveguides with differing ground wavelengths. The cross section of the waveguides does not need to be exactly right-angled, but rather rounded right angle geometries; elliptical waveguides can also be used.
The asymmetrical arrangement of the waveguides, which is common to the various implementations, causes the formation of a hybrid wave type in the transformation stage, which brings about the transformation.